1. Field of the Invention
The present invention relates to a method for selectively separating ethylene from a mixed gas by forming an ethylene-hydroquinone clathrate.
2. Description of the Related Art
When the catalytic pyrolysis of naphtha is performed, various types of gases are generated, which are then separated and recovered, respectively, to obtain various necessary components. The main components of naphtha pyrolysis gas include hydrogen, nitrogen, methane, ethane, ethylene, propane, propylene, carbon dioxide, etc. Among these components, most hydrocarbons have low boiling points and are not easily separated because of their close boiling points. There are several methods developed to separate the hydrocarbons, but it can be said that deep freezing distillation is almost the only method currently available that is economically feasible and can provide high throughput.
However, even with the use of the deep freezing distillation, it is not easy to separate ethylene contained in the pyrolysis gas. In general, the method for recovering ethylene from the pyrolysis gas begins by separating C4+ hydrocarbons having relatively high boiling points, and then has a step for separating C1 hydrocarbon (methane) and hydrogen. The separation of C2 and C3 hydrocarbons is the final stage of the recovery process. Among these steps, it is very difficult to separate ethane and ethylene because of their small differences in relative volatilities.
Ethylene is the smallest unit of hydrocarbons containing a double bond and is the major product of the petrochemical industry. Various copolymers can be produced by polymerization using the double bond of ethylene or reaction between the double bond of ethylene and other substances, and thus its application is very wide in petrochemical industry. As a result, it is necessary to develop a method for effectively and economically separating effective substances such as ethane and ethylene from the pyrolysis gas. Therefore, a significant improvement in process productivity and economics is expected when yield and efficiency of the process are improved and energy consumption is reduced even by a small margin compared to the conventional deep freezing distillation, considering the scale of the process.